The invention relates to a burner for use in the partial combustion of carbonaceous fuels, and particularly for the partial combustion of finely divided solid fuel such as pulverized coal, in which the fuel is introduced together with an oxygen-containing gas into a reactor space operating under a pressure up to 100 bar for producing pressurized synthesis gas, fuel gas or reducing gas.
Partial combustion, also known as gasification, of a solid carbonaceous fuel is obtained by the reaction of the fuel with oxygen. The fuel contains as combustible components, mainly carbon and hydrogen, which react with the supplied oxygen--and possibly with any steam and carbon dioxide as may be present--to form carbon monoxide and hydrogen. At some temperatures it is also possible to form methane.
There are in principle two different processes for the partial combustion of solid fuel. In the first process, solid fuel in particulate form is contacted with an oxygen-containing gas in the reactor in a fixed or fluidized bed at a temperature below about 1000.degree. C. A drawback of this method is that not all types of solid fuel can be partially combusted in this manner. For example, high swelling coal is unsuitable since particles of such coal type easily sinter, resulting in risk of clogging of the reactor.
A more advantageous process passes the finely divided fuel in a carrier gas such as nitrogen or synthesis gas into a reactor at relatively high velocity. In the reactor a flame is maintained in which the fuel reacts with oxygen-containing gas at temperatures above 1000.degree. C. The carbonaceous fuel is usually passed into the reactor via a burner, and the oxygen-containing gas is also passed via the burner into the reactor. In some processes a moderator gas such as steam or carbon dioxide is also passed via the burner to the reactor; such a moderator gas is often advantageous for reducing or preventing premature contact of the oxygen with the reactor gas, which might result in undesirable complete conversion of the reactor gas.
The present burner is well suited to introduce the reactants in any desired manner, i.e., vertically or horizontally, into the reaction zone of a conventional, refractory lined partial oxidation gas generator, and is particularly suited for use in solid fuel gasification apparatus having a plurality of burners for the reactants positioned on substantially opposite sides of the combustion zone, whereby the reactants are introduced horizontally and the burner jets impinge on each other to facilitate the partial oxidation process and to minimize erosion of the refractory wall.
Since flame temperatures may reach 2000.degree. C. or more, a primary concern of such burners is to prevent damage to the burner front, also referred to as the burner face, caused by the high heat flux during the gasification process. To protect the burner front from overheating, it has been suggested to provide a refractory lining applied to the outer surface of the burner front wall and/or provide a hollow wall member with internal cooling passages through which cooling fluid is circulated at a rapid rate. The present invention provides an improved burner wherein the cooling fluid is used to flow in a particular manner to assure even cooling of the burner front face so as to minimize thermal stresses which could cause deterioration and even failure of the burner during prolonged operation.